fix: memory allocation method (#1220)

* Fix : memory allocation method

"new" is not used in C , because of that the compiler was giving compilation error.
Instead malloc was used for memory allocation.

* updating DIRECTORY.md

* Update data_structures/graphs/kruskal.c

Co-authored-by: Stepfen Shawn <[email protected]>

* updating DIRECTORY.md

---------

Co-authored-by: github-actions[bot] <[email protected]>
Co-authored-by: Stepfen Shawn <[email protected]>

Author: 3 people

data_structures/graphs/kruskal.c

@@ -27,11 +27,11 @@ struct Graph
 // Creates a graph with V vertices and E edges
 struct Graph *createGraph(int V, int E)
 {
-    struct Graph *graph = new Graph();
+    struct Graph* graph = (struct Graph*)(malloc(sizeof(struct Graph)));
     graph->V = V;
     graph->E = E;
 
-    graph->edge = new Edge[E];
+    graph->edge = (struct Edge*)malloc(sizeof(struct Edge) * E);
 
     return graph;
 }

leetcode/DIRECTORY.md

@@ -27,7 +27,7 @@
 |   24 | [Swap Nodes in Pairs](https://leetcode.com/problems/swap-nodes-in-pairs)                                                                               | [C](./src/24.c)   | Medium     |
 |   26 | [Remove Duplicates from Sorted Array](https://leetcode.com/problems/remove-duplicates-from-sorted-array)                                               | [C](./src/26.c)   | Easy       |
 |   27 | [Remove Element](https://leetcode.com/problems/remove-element)                                                                                         | [C](./src/27.c)   | Easy       |
-|   28 | [Find the Index of the First Occurrence in a String](https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string)                 | [C](./src/28.c)   | Medium     |
+|   28 | [Find the Index of the First Occurrence in a String](https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string)                 | [C](./src/28.c)   | Easy       |
 |   29 | [Divide Two Integers](https://leetcode.com/problems/divide-two-integers)                                                                               | [C](./src/29.c)   | Medium     |
 |   32 | [Longest Valid Parentheses](https://leetcode.com/problems/longest-valid-parentheses)                                                                   | [C](./src/32.c)   | Hard       |
 |   35 | [Search Insert Position](https://leetcode.com/problems/search-insert-position)                                                                         | [C](./src/35.c)   | Easy       |